Compound Stops in Mother Church Organ of Christian Science
By LAWRENCE I. PHELPS
[Mr. Phelps was commissioned by the authorities of the Christian Science Church to supervise the design and construction of the great new organ of whose resources he writes.]
The stoplist of the new organ in The Mother Church, The First Church of Christ, Scientist, in Boston, built by the Aeolian-Skinner Company was published in these pages in the July issue along with a general description of the tonal resources and outstanding features of the instrument. Publication of this information seems to have inspired a genuine interest among students and practitioners of tonal design and many requests have been received for additional information. Inasmuch as most of this interest seems to enter in the compound stops it is hoped that the following information regarding these stops will prove helpful.
There are twenty-six harmonic-corroborating compound stops in the instrument. One hundred and eight of the 235 ranks of pipes which comprise the tonal resources of the organ are contained in the compound stops. Together these stops total 6,051 pipes. The compound stops fall roughly into three groups. The first of these is that of the “full mixture” variety. The primary purpose of these stops is to impart power and richness to the ensemble rather than brilliance. The great full mixture, the swell plein jeu, the bombarde grande fourniture and the pedal fourniture are examples of this type. The second group are those whose purpose is primarily to impart brilliance while improving the clarity and definition of all combinations into which they enter. Among the stops of this type are the hauptwerk mixture and scharf and the positiv scharf and zimbel. In the third group are those stops which are used primarily alone as solo stops or which, together with other stops, form combinations especially suited for solo use. Among these are the positiv and bombarde cornets, the choir sesquialtera and carillon and hauptwerk sesquialtera.
There are other stops which do not fall strictly into any one of these groups. Their functions are common to two, and in some cases all three, of the groups. A good example of these is the great cornet, which, although it is suited for use as a solo stop, also functions admirably as a stop of the first group, adding richness and power to the full great ensemble. The great scharf, which by nature of its construction might be primarily considered a stop for imparting brilliance to the great ensemble, also adds considerable power to the ensemble.
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The motives of the designer in endowing this organ so richly with compound stops were several. First among these was the wish to create an instrument in which each division would be complete and in every way independent and in which octave couplers, though included as recognized and legitimate mechanical aids, would be entirely unnecessary to the total design. Some might ask: “But couldn't this result be gained just as well through the use of a greater number of independent ranks instead of compounding so many ranks together?” While the writer acknowledges the possibility of achieving divisional independence through the use of many independent ranks, and heartily recommends this practice in the design of small instruments, it is his considered opinion that real cohesion of ensemble cannot be produced by independently winded ranks of pipes. (Independently winded ranks of pipes refers here to the practice of using one chest valve per note.) He is convinced that well intergraded and truly musical results are possible only when pipes are winded from a common channel or key chamber. It is quite possible to apply the key chamber to the pitman type windchest, and this was accomplished very successfully through the skill of Aeolian-Skinner craftsmen. However, with pipes standing on common chambers over pitman chest action, it is not practical to attempt such independent control of the ranks as can easily be attained in the more usual type of “barred” windchests - slide chests, for example. Therefore it can be stated that the use of many influential compound stops was adopted in the case at hand as a device for effecting the greatest possible cohesion in the ensemble with the minimum of mechanical complication. It should be pointed out, however, that the time consumed in the tonal finishing of this instrument occupied about eight months and this should warn that the devices used here should not be attempted elsewhere unless accompanied by an equal determination to see the work through to its glorious conclusion.
As the organ is now finished and has been in use for six months the various elements of its design are no longer academic issues, and although the following discussion of the most important features and functions of each stop is concerned primarily with the designer's point of view, it should be remembered that the occasional remarks as to the merit of this of that effect are made by one who has been privileged to hear the instrument many times each week in the actual playing of a great variety of music since it first went into service.
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The scaling of the hauptwerk is based on the 8-ft. prinzipal, which has a diameter of five and five-eighths inches at low C and continues to the top according to to a fairly rapid decreasing diameter scale. The scale of each successive independent rank comprising the principal “chorus” begins proportionately smaller than the 8-ft. prinzipal in the bass but continues progressively slower, so that as these stops ascend the diameters of the pipes gradually become equal to the pipes of similar pitch in the 8-ft. prinzipal and eventually, as the treble is reached, attain diameters which surpass those of the 8-ft. prinzipal. For example: the diameter of low C of the 4-ft. oktav is one semi-tone smaller than the 4-ft. C of the 8-ft prinzipal, and by the time the 4-ft. oktav has advanced through three octaves, the diameter of treble C is one full semi-tone larger than the pipe of similar pitch in the 8-ft prinzipal. The 2-ft. superoktav, which begins at low C two semi-tones smaller in diameter than middle C of the 8-ft. prinzipal, a pipe of similar pitch, has become, by the time it reaches treble C, three semi-tones larger than high C in the 8-ft. prinzipal, which again is a pipe of similar pitch. This principle is applied in the same way to each rank of the chorus.
The bass and tenor of the ranks constituting the upper work of the chorus must be suppressed in order that they may not become assertive and that they blend well with the 8-ft. prinzipal. The treble of these ranks must not be too thin in color or they will seem to screech and produce a disagreeable effect. Therefore this system of scaling is necessary in order that the supression of the strength of the upper-work in the lower end does not produce a too fluty tone, resulting in a thickening effect, while the trebles, due to the necessity for increase to make contrapuntal playing clear, do not become too thin and scratchy, producing the screamy effect so often objected to.
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The compositions of the three hauptwerk compound stops is as follows:SESQUIALTERA II 122 Pipes 12 - 17 = 49 notes 10 - 12 = 12 " ___ 61 MIXTUR IV-VI 287 Pipes 15 - 19 - 22 - 26 = 18 notes 12 - 15 - 19 - 22 = 12 " 8 - 12 - 15 - 19 - 19 = 12 " 1 - 8 - 12 - 12 - 15 - 15 = 12 " 1 - 8 - 8 - 12 - 12 = 7 " ___ 6l SCHARF IV-VII 318 Pipes 22 - 26 - 29 - 33 = 12 notes 19 - 22 - 26 - 29 = 12 " 15 - 19 - 22 - 26 - 26 = 6 " 15 - 19 - 22 - 22 - 26 - 26 = 6 " 12 - 15 - 19 - 19 - 22 - 22 = 6 " 12 - 15 - 15 - 19 - 19 - 22 - 22 = 6 " 8 - 12 - 15 - 15 - 19 - 19 = 6 " 1 - 8 - 12 - 12 - 15 - 15 = 7 " ___ 61
The compound stops follow exactly the same principle of scaling, except that they begin much smaller than the 8 ft. prinzipal and the increase toward the treble is such that the diameter scales of the 8-ft. prinzipal are equaled but not surpassed; the effect being that the individual ranks in the mixtures have a thinner and less powerful tone than the independent ranks of similar pitch. The whole object of this scaling method is to produce a clear ensemble for contrapuntal playing. Clarity in the lower end is provided by a closely-knit, brilliant color in which no single rank becomes more prominent than the 8-ft. prinzipal, but all ranks contribute to color the 8-ft. prinzipal. As we ascend toward the treble the color changes, becoming fuller and stronger, but never aggressive or screamy. This results in beautiful, well-balanced clarity in fugue playing. The upper voice is always audible because of its fullness and superior strength. The inner and lower voices are clear due to their rich color rather than by the protrusion of the ranks of higher pitch. The mixtur, when added to the ensemble produces the effect of added fullness in the treble while brightening the lower end. The scharf adds a sheen to the entire ensemble, and, due to the care with which it is regulated, the lower end never seems over-assertive. This the scharf does not destroy the clarity, but rather adds a nearly equal sheen throughout the compass.
The sesquialtera, though usable in the chorus is primarily useful in smaller combinations and is intended especially for use in solo combinations with the flutes. The seventeenth has been regulated especially with the thought in mind of avoiding, as much as possible, disagreeable cross-relations which sometimes occur in trio playing. Thus this stop is especially satisfactory in the playing of trio-sonatas, in which it works equally well for either of the manual parts
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The composition of the two positiv mixtures is a follows:SCHARF IV-VII 337 Pipes 22 - 26 - 29 - 33 = 6 notes 19 - 22 - 26 - 29 = 6 " 15 - 19 - 22 - 26 = 12 " 12 - 15 - 19 - 22 - 22 = 6 " 12 - 15 - 19 - 19 - 22 - 22 = 6 " 12 - 15 - 15 - 19 - 19 - 22 - 22 = 6 " 8 - 12 - 12 - 15 - 15 - 19 - 19 = 6 " 1 - 8 - 8 - 12 - 12 - 15 - 15 = 13 " ___ 61 ZIMBEL III 183 Pipes 36 - 40 - 43 = 6 notes 33 - 36 - 40 = 6 " 29 - 33 - 36 = 6 " 26 - 29 - 33 = 6 " 22 - 26 - 29 = 6 " 19 - 22 - 26 = 6 " 15 - 19 - 22 = 12 " 12 - 15 - 19 = 6 " 8 - 12 - 15 = 7 " ___ 61
These two positiv mixtures are scaled along lines similar to those used in the hauptwerk, but they are based on the 4-ft. harmonic series. The mouths of the pipes in these mixtures are cut very low, an average cut-up of about one-sixth for all ten ranks, and the languids are virtually without nicking. The scharf, due to its small-scale low cut-up, doubled ranks and absence of nicking produces a glow and warmth not always evidenced in mixtures of this type. It can be used in chorus with either the flutes or the principals. When playing fugue episodes on the positiv, in contrast to the hauptwerk, the scharf is especially useful.
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The zimbel is not strictly a chorus mixture. The tone of the individual pipes in this stop is somewhat more fluty than that of the principals. It can be used in chorus, with or without the scharf, but it is more effective when used in light combinations with the flutes or when used with only one of the ranks of principal tone in the combination. This stop actually can be used in combination with any of the three 8-ft. stops, without any intermediate pitches being present and without fear of the results. Of course it is especially good in fast-moving music, where its effect is quite bell-like.
The cornet is primarily a solo stop. The pitches of its five ranks are 8, 4, 2 2/3 and 1 3/5-ft. They are completely without breaks with the exception that the 1 3/5-ft. repeats at top G sharp. The 8-ft. rank is a gedeckt. All the other ranks are open. The cut-up of all open ranks is no higher than one-fifth and nicking is used only in the bass. The 2 2/3-ft., 2-ft. and 1 3/5-ft. ranks are tapered slightly in the bass, the taper becoming less as the pipes ascend, and all ranks are straight, without taper, in the treble. The scales of the pipes at low C are as follows: 8-ft. = 4 15/16"; 4-ft. = 4 1/8"; 2 2/3-ft. = 3 7/16" at the mouth, tapered to 2 7/8" at the top of the pipe; 2-ft. = 2 11/16" at the mouth, tapered to 2 7/16" at the top; 1 3/5-ft. = 2 1/4" at the mouth, tapered to 2 1/16" at the top. The scales of all ranks are special irregular scales and do not correspond to any standard halving ratio. The fact that this stop continues from low C to the top, instead of beginning at middle C or tenor G, as many classical examples do, makes it very useful in many ways not previously imagined. It is especially good for figurations in the left hand in certain old music, particularly in variations, and there is a great wealth of music written especially for the cornet stop by such as Couperin, Clerambault, Gibbons, Cornet and Sweelink. The cornet has a clear tone and individual character which gives it a penetrating effect that makes possible its use as a solo voice., with accompaniments which seem to strong for it when compared note for note. This makes the stop especially useful in playing chorale preludes of various types. Due to the careful scaling and regulation of the pipes, this stop can be used down to its lowest note without any disagreeable separation of the ranks. It is not a powerful stop, being perhaps equivalent in strength to the swell oboe. It is much different in character from the cornet effect made up by drawing individual ranks in the positiv. One of the reasons for this is that all of the ranks of the cornet stand on a key-chambered table and thus all the ranks of each note have a common wind supply. This produces a wonderfully blended effect and the five ranks speak truly as one stop. The scaling of the cornet is much bolder than individual positiv ranks.
In every case where the pitch has been duplicated by an additional rank in the mixtures throughout the organ the added rank is two semi-tones smaller in scale and is provided with extra-long feet. This was done as an aid to tuning as it reduces the tendency of closely placed ranks of similar pitch to quarrel.
The compositions of the great compound stop are:FULL MIXTURE IV 244 Pipes 12 - 15 - 19 - 22 = 12 notes 8 - 12 - 15 - 19 = 12 " 1 - 8 - 12 - 15 = 37 " ___ 61 " SCHARF IV 244 Pipes 19 - 22 - 26 - 29 = 18 notes 15 - 19 - 22 - 26 = 12 " 12 - 15 - 19 - 22 = 18 " 8 - 12 - 15 - 19 = 6 " 5 - 8 - 12 - 15 = 7 " ___ 61 " CORNET IV-VI 309 Pipes 12 - 15 - 17 - 19 = 12 notes 8 - 12 - 15 - 17 - 19 = 19 " 1 - 8 - 12 - 15 - 17 - 19 = 17 " 1 - 8 - 12 - 15 = 14 " ___ 61 "
Low C of the great 8-ft. principal measures approximately 6 1/16 inches in diameter. The scale of this stop, as well as that of the prestant, is irregular, not falling exactly into any of the normal halving ratios. The largest pipe of low C, of the full mixture has a diameter of approximately 2 1/2 inches and this stop progresses according to a ratio halving on the nineteenth. The largest pipe on low C of the scharf is approximately 1 5/8 inches in diameter and the scale of this stop halves on the eighteenth. The cornet is based on an 8-ft. C equivalent to a standard 43-scale and proceeds according to a strict half on the eighteenth ratio for all ranks.
As mentioned in the article in the July issue, the principal chorus of the great is all 2/7-mouthed. This includes the 8-ft. principal, the 4-ft. prestant, the full mixture and the scharf. In previous examples where 2/7-mouthed pipes have been used “parallel” scaling and voicing technics have been used. This means that every pipe of similar pitch throughout the chorus has the same diameter and is voiced to the same strength. In the present case the rule of “parallel” strength was followed so far as possible, but special attention was given to making the pipes as “un-parallel” in scale as possible. In other words, the chorus was designed so that no pipe of the same pitch would be likely to have exactly the same diameter. This was done primarily for the purpose of producing smoother and more accurate tuning.
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It will be interesting perhaps to note that while the stoplist gives the impression that there is only one 8-ft. principal on the great, it is obvious upon examining the composition of the mixtures that beginning with middle C there are actually three 8-ft. principal ranks. The 8-ft. rank in the full mixture is approximately equivalent to a 45-scale 2/7-mouthed principal and the 8-ft. rank in the cornet is approximately equivalent to a 43-scale 1/4 mouthed principal. Thus we have here actually a first, second and third principal. Of course, according to correct usage, it is impossible to have more than one principal on any one manual, so we shall have to call them diapasons when thinking of them in this light. This strong presence of 8-ft. tone, plus the use of expansion chambers in the top boards of all these stops, produces a rich, full, though brilliant, ensemble.
The idea of parallel voicing for the 2/7-mouth chorus was carried out only to a limited extent. The lower ends in the mixtures were somewhat suppressed so that they would not walk off with the show. This is one of the reasons for using a fairly slow halving ratio for these mixtures so that the scales in the bass end would not be too large and thus produce a thick tone when controlled as carefully as they have been here. The absence of an independent twelfth and fifteenth, though pointed out by some who have only examined the stoplist, has never been mentioned by anyone who has tried the instrument. Under actual playing conditions, when progressing from 8-ft. principal to full great, the full mixture, when added to the 8-ft. principal and 4-ft. prestant, seems to be the next logical step.
This proves, to a certain extent at least, that an independent twelfth and fifteenth would be too subtle in effect to be of much use.
The scharf has truly amazing powers for blending with the rest of the ensemble and when drawn has the effect of simply turning on more light. One never becomes conscious of individual pipes, as is so often the case with high-pitched mixtures of this sort. It can be used with equally good effect either in sustained or in contrapuntal playing.
The cornet is a very useful stop. It does not break in the usual sense of the word, but merely adds ranks as it ascends and omits two ranks in the top octave. Due to the fact that the stop runs without a break of any kind from tenor F to treble A sharp, it can be used for many of the usual solo cornet effects. Being made entirely of principal pipes, and containing the nineteenth, it is especially well suited for solo playing against a fairly substantial accompaniment. Used with the 8-ft. holzflöte or 8-ft. principal, to fill in the 8-ft. pitch in the lowest octave, the stop provides a complete secondary great chorus. When added to the 2/7-mouth chorus this stop adds a reediness (due to the presence of the nineteenth) and richness to the ensemble while not obscuring the moving voices in the way reeds often do. Thus the absence of reeds on the great does not become an issue.
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The compound stops of the bombarde are composed as follows:GRANDE FOURNITURE VI 366 Pipes 12 - 15 - 19 - 22 - 26 - 29 = 6 notes 8 - 12 - 15 - 19 - 22 - 26 = 18 " 1 - 8 - 12 - 15 - 19 - 22 = 18 " 1 - 8 - 8 - 12 - 15 - 19 = 6 " 1 - 5 - 8 - 8 - 12 - 15 = 6 " 1 - 1 - 5 - 8 - 8 - 12 = 7 " ___ 61 SCHARF III 183 Pipes 29 - 33 - 36 = 18 notes 26 - 29 - 22 = 6 " 22 - 26 - 29 = 6 " 10 - 22 - 26 = 6 " 15 - 19 - 22 = 6 " 12 - 15 - 19 = 6 " 8 - 12 - 15 = 13 " ___ 61 HARMONICS VIII 478 Pipes 15 -17 - 19 - 21b - 22 - 23 - 24 - 25 = 44 notes 8 -10 - 12 - 15 - 17 - 19 - 21b - 22 = 5 " 1 - 5 - 8 - 10 - 12 - 15 - 17 - 19 = 7 " 1 - 5 - 8 - 1 - 12 - 15 = 5 " ___ 61 "
The bombarde is unusual for a division of this type in that it is designed to do its job without the necessity of forcing the reeds. The reeds are scaled and voiced normally for 4-inch wind pressure, with open French type shallots. This makes it possible to add these reeds to the great or hauptwerk or to the full swell without obliterating the flue work of these divisions and also makes better balance when playing these reeds antiphonally against the great or swell.
The compound stops in the bombarde have been designed expressly for the purpose of reinforcing the bombarde reeds and of building up the power of the bombarde division so that the bombarde tutti is more powerful and reedy, in effect, than that of any other division. It is quite possible when used at full strength, to play a solo on the bombarde against the full great and swell coupled together; yet when the full bombarde organ is added to the full great, there is no blotting out of the great as sometimes happens.
The bombarde cornet is the only stop in the division which could not be considered strictly part of the bombarde chorus. This stop has the same composition as the positiv cornet. It is larger (about two semitones) in scale but it progresses according to identical ratios. The tapering of the pipes in the bass is exactly in proportion to that used in the positiv cornet, but the voicing treatment of this stop is much different. To begin with, this cornet stands on higher wind pressure than the one in the positiv, the pressure for all of the bombarde pipes being 4 inches. The voicing treatment is in keeping with this. The cutups are somewhat what higher and all languids are nicked except in the trebles. The effective strength of the stop when heard out in the building is at least double that of the positiv cornet. The strength of its individual ranks has been carefully intergraded, so that, from top to bottom, no rank is assertive. The stop can be used antiphonally with its little brother on the positiv or it can be used as a solo against full hauptwerk or, for that matter, against a fairly substantial great. This stop has proved to be one of the most generally useful solo stops in the organ and many uses have been found for it which the designer must admit he did not have in mind when including it in the disposition. For example, the figurations in the left hand beginning with the eighth measure of the piu mosso of the second movement of Guilmant's Fifth Sonata (Op. 80) make much better sense when soloed on this stop than when played as indicated. A very striking effect can be produced by soloing on the cornet combined with the harmonics. This is particularly good in the tenor and middle registers. It is a very penetrating effect, somewhat like that of a big French type trumpet, and indeed, has been mistaken for a trumpet by several listeners.
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The harmonics is truly a remarkable stop. Note that it contains all of the harmonics of the 8-ft. series from the third to the tenth inclusive. Used in the bombarde ensemble it gives the division a color which sets it off completely from the rest of the organ. Combined with the full organ fluework, it adds a blaze of reed-like color without in the least harming the transparency of the ensemble. The scaling of this stop is quite different from that normally used for stops of this sort in that all of the pipes are based on the same scale, which is standard 42-scale, at 8-ft. C, one-half on the eighteenth. The difference in color and strength required for the various ranks is obtained through differences in mouth widths and voicing treatment.
The grand fourniture is actually a whole chorus in itself and when used with the 8-ft. principal to supply the necessary 8-ft. and 4-ft. pitches in the lower octaves produces a rich flue chorus which can be used in contrast with the great. The scharf is made to top off the entire bombarde ensemble, but it can be used satisfactorily with the grand fourniture and the 8-ft. principal to produce a fourth manual foil to the great full through scharf. The diameter of the largest pipe in the grand fourniture is 2 5/8 inches, that in the scharf is 7/8 inches and the ratio of both stops is one-half on the ninteenth.
The 8-ft. principal is really a compound stop composed of an 8-ft. rohrflöte, measuring about 5 5/16 inches on low C and continuing according to an irregular scale, and a 4-ft. rank, based on a low C of standard 54-scale and halving on the eighteenth. Both ranks have one-quarter mouths. The rohrflöte rank has chimneys throughout.
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The following are the compositions of the swell compound stops:SESQUIALTERA III 183 Pipes 12 - 15 - 17 = 54 notes 5 - 8 - 10 = 7 " ___ 61 PLEIN JEU IV 366 Pipes 12 - 15 - 19 - 22 - 26 - 29 = 12 notes 8 - 12 - 15 - 19 - 22 - 26 = 12 " 1 - 8 - 12 - 15 - 19 - 22 = 12 " 1 - 8 - 8 - 12 - 15 - 19 = 12 " 1 - 5 - 8 - 8 - 12 - 15 = 6 " 1 - 1 - 5 - 8 - 8 - 12 = 7 " ___ 61 " CYMBALE IV 244 Pipes 26 - 29 - 33 - 36 = 12 notes 22 - 26 - 29 - 33 = 6 " 19 - 22 - 26 - 29 = 6 " 15 - 19 - 22 - 26 = 6 " 12 - 15 - 19 - 22 = 6 " 12 - 15 - 15 - 19 = 6 " 8 - 12 - 15 - 15 = 19 " ___ 61 " FOURNITURE III 183 Pipes 19 - 22 - 26 = 12 notes 15 - 19 - 22 = 18 " 12 - 15 - 19 = 12 " 8 - 12 - 15 = 6 " 1 - 8 - 12 = 13 " ___ 61
It will be noted that except for slight differences in breaking the composition of the swell plein jeu is the same as that of the bombarde grand fourniture. The effect, however, is much different, since it is in a swell-box and scaled much smaller. There is nothing unusual about the scaling of the swell flue chorus. The sesquialtera and the plein jeu are allowed to speak up a little more in the tenor and bass than are the mixtures in the rest of the organ. This is done so that they will better complement the swell reeds. The cymbal tops off the whole swell, performing all the functions usual to its office. The 8-ft. diapason, the 4-ft. octave and the sesquialtera are slotted, these being the only slotted chorus flue pipes in the entire organ. The diapason is 5 13/16 inches in diameter at low C and proceeds according to a ratio halving on the eighteenth and all of the swell flue work is scaled accordingly. The sesquialtera is not by any means a timid stop, but is voiced very full, and, as a matter of fact together with proper selection of 8-ft. and 4-ft. stops makes a very fine cornet equaling the swell 8-ft. trompette in strength.
This brings to mind a young organist of note who after playing this instrument for some time, was overheard to say: “This is the only organ I ever saw on which one could produce a crescendo on cornets”. As a matter of fact his observation was quite correct; the cornet effect is available on at least seven different dynamic levels and in a large variety of color nuances.
The little three-rank fourniture, which is based on standard 48-scale halved on the eighteenth, is a very useful stop. It can he used in combinations with the flutes or in small chorus combinations producing antiphonal effects with the hauptwerk, positiv or great.
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The sesquialtera in the choir is composed of two open flutes. The 2 2/3-ft. measures about 2 9/16 inches on low C. The 1 3/5-ft. measures about 2 1/16 inches on low C. In the lowest octave the pipes of both ranks are very slightly tapered to encourage prompt speech, but by middle C all the taper has been gradually worked out and from there on the pipes are straight. Both ranks have one-fifth mouth widths. The 1 3/5-ft. repeats at top G sharp. Being quite soft, this stop can enter into many different solo combinations with the choir flutes, strings or the clarinet, and is a very useful color-producing stop. Here again the cornet can be produced by drawing the sesquialtera with the 2-ft. zauberflöte, 8-ft. lieblich gedeckt and 4-ft. lieblich flöte. With a choice of other 8 and 4-ft. stops a cornet of quite different color can be produced.
The carillon contains a 4-ft. rohrflöte measuring about 3 9/16 inches at low C, a 1 3/5-ft. nachthorn measuring approximately 2 1/16 inches at low C and a 1-ft. rank, also composed of nachthorn type pipes, measuring about 1 9/16 inches at low C. The rohrflöte rank is scaled according to a normal rohrflöte ratio and it has chimneys throughout. The pipes of the 2 2/3 and 1-ft. proceed according to a special irregular scale worked out for this stop. Both these ranks repeat in the top octave. This stop is especially well suited to the name as it actually does sound bell-like when played in rapid passages. Special care was taken with both the sesquialtera and the carillon so that the higher pitch ranks do not separate too much in the bass and tenor.
The two compound stops in the solo organ are both old, the plein jeu being the old great mixture, with the tierce removed, and the harmonia aetheria being exactly as it was in the old organ, with minor revoicing. The 8-ft. rank in the latter is made of wooden bourdon pipes for two octaves and then becomes open metal, and the sub-octave rank, which begins at middle C, is composed of wooden bourdon pipes throughout. This stop is best used in full string combinations. The plein jeu together with the 8-ft. principal and 4-ft. prestant, which are also from the old great organ, produce a principal chorus which contrasts remarkably with those in the other divisions of the organ. The compositions of these two stops follow:PLEIN JEU IV 244 Pipes 12 - 15 - 19 - 22 = 12 notes 8 - 12 - 15 - 19 = 24 " 1 - 8 - 12 - 15 = 25 " ___ 61 " HARMONIA AETHERIA III-V 269 Pipes 1 - 8 - 15 = 12 notes 1 - 5 - 8 - 15 = 12 " sub 8 - 1 - 5 - 8 - 15 = 37 " ___ 61 "
The compound stops in the pedal organ are composed as follows:GRAND CORNET V (32-ft. series) 96 Pipes 19 - 21 flat - 23 = 32 notes Plus 10 2/3' Grossquinte and 6 2/5' Grossterz CORNET IV (16-ft. series) 128 Pipes 17 - 19 - 21 flat - 22 = 32 notes FOURNITURE IV (16-ft. series) 128 Pipes 12 - 15 - 19 - 22 = 32 notes MIXTUR III (16-ft series) 96 Pipes 15 - 19 - 22 = 32 notes SCHARF IV (16-ft. series) 128 Pipes 26 - 29 - 33 - 36 = 32 notes
The fourniture is really a pedal full mixture, being a strong mixture of the chorus type. The smaller mixtur III is less strong and is especially designed for use with the hauptwerk and the lighter manual ensembles. The scharf is a real crowning stop, like its manual counterparts, and is used primarily with full pedal ensembles. The scale of the pedal 8-ft. principal is standard 42, one-half on the seventeenth, and all the pedal compound stops are scaled accordingly.
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The cornet IV is composed of four ranks, all quite different in construction. The first rank is a tapered flute conique, the second is a rohrflöte, the third is made of slim nachthorn pipes, while the 2-ft. is a tapered blockflöte. These four ranks combine in such a way as to produce a beautifully clear pedal line when used in light pedal combinations. It has been noted by some that this stop sounds quite fagotto-like, but actually its tone is much more transparent than can be produced by reed pipes. The 16-ft. resultant tone produced by these four ranks is so successful that the 16-ft. bourdon has little effect when added to it. Through the use of this stop with others of the softer pedal stops, the pedal line is always clearly independent although not necessarily loud.
The grand cornet draws also the independent 10 2/3 ft. and 6 2/5-ft. Together these five ranks produce a transparent 32-ft. effect which has proved to be highly useful. The diameters and mouth widths of the low C's of the five ranks that make up this stop are as follows: 10 2/3-ft. = 8 3/16 inches, 2/9 mouth; 6 2/5-ft. = 4 15/16 inches, tapered 2/3, 2/9 mouth; 5 1/3-ft. = 4 11/16 inches, 2/9 mouth, 4 4/7-ft. = 3 inches, 1/5 mouth, 3 5/9-ft. = 2 9/16 inches, 1/6 mouth. The ratio of all ranks is one-half on the seventeenth.
It is never a problem to make the pedal heard clearly at all dynamic levels without the use of manual to pedal couplers. As a matter of fact, the couplers to the pedal have been virtually unused. The effect of a pedal division which is so completely independent is something which must be heard to be understood.